In the transportation sector, spring brake mechanisms are widely recognized as a safe and reliable means of stopping heavy trucks and large commercial vehicles (the terms “vehicle” and “truck” shall be used interchangeably herein). Spring brakes use compressed air to make the brakes work: they are applied when air pressure is released, and disengaged when air pressure is supplied. Generally, a brake drum mechanism of a truck or equivalent spring brake vehicle is fixed on an axle for synchronous rotation, as depicted in FIG. 1.
FIG. 1 shows a conventional S-cam braking mechanism 10 mounted relative to axle 12. A pair of oppositely positioned brake shoes 14 is provided wherein each shoe is typically a steel mechanism with a lining 16 that causes friction against a brake drum 18. Brake shoes 14 have hook holes bored therein (not shown) to accommodate attachment of a stiff return spring 20 thereto. A pair of cam rollers 22 is provided for cooperation with an S-shaped cam (“S-cam”) 24 that pushes brake shoes 14 apart and against brake drum 18 during a braking operation. Return spring 20 connected to each brake shoe 14 returns the shoes to an open position when not spread by the S-cam (or, alternatively, a diaphragm, not shown). A brake chamber 26 is provided as a generally cylindrical container that houses a slack adjuster 28. Slack adjuster 28 connects a push rod 30 to S-cam 24 for adjustment of a distance between the brake shoes, wherein such adjustment moves S-cam 24. Upon extension of push rod 30, the brakes are applied. Upon release of push rod 30, the brakes are released.
Spring brakes were designed so there would always be a fail-safe method of stopping an air brake vehicle, if for some reason, all air supply pressure were suddenly lost while the vehicle is in motion. This forms an emergency brake action to stop a vehicle in motion should the air supply fail. A parking brake valve (for instance, on the cab dash) releases the air pressure in the spring brake chambers, and the powerful spring applies hundreds of pounds of brake force on the push rod, thereby actuating the slack adjuster and setting the brakes.
When the brakes are used, the brake shoes force the brake linings to move outward and press the inner sides of the brake drum and thus produce a great frictional force to reduce truck speed or stop the truck altogether. These brake linings will gradually degrade after repeated use, and the brake shoes must be replaced in order to maintain the function of the braking system and ensure safety of driving. During the course of brake maintenance, it becomes necessary to remove the return spring from the brake shoe, although elevated tension in the spring (as much as 2,500 lb) renders this task difficult and dangerous.
Tools relating to brake springs tend to focus on different methods of gripping the brake spring. Some tools provide ease of use and/or construction simplicity. Some brake tools use a simple V-shaped cut with which to push on the spring. This allows an unsecured hold on the spring that sometimes results in inadvertent release of the spring. Such a slip can be dangerous to the repair person. Improved tools combine modified V-shaped cuts or other solutions for removing brake springs.
One known brake tool for assisting brake technicians in the removal and installation of S-cam brake shoes is disclosed by U.S. Pat. No. 7,676,896 to Carscadden. Carscadden discloses a brake tool having an elongate shaft having an upper end with an elongated, tapered neck and a narrow, flattened stem at a distal end thereof. A C-shaped gripping member is attached to the stem and provided co-planar therewith for gripping of a return spring thereby. A technician uses the S-cam as a fulcrum for the shaft to thereby stretch the return spring as needed for removal and attachment during brake servicing.
Carscadden, like other prior art, does not address the need for brake technicians to not only have an efficient means of maintaining S-cam braking mechanisms but also for such technicians to do so reliably and safely. There exists a need to provide a tool for servicing the S-cam brake assembly in a reliable and secure manner, regardless of the support surface on which the brake assembly is mounted (i.e., on an axle, on a table or like support surface, etc.). Such a tool should be readily fabricated from commercially available materials and amenable for use with existing commercially available braking mechanisms. The present invention now satisfies these needs.